The semiconductor industry is constantly driven to increase the operating speed of integrated circuit devices, e.g., microprocessors, memory devices, and the like. This drive is fueled by consumer demands for computers and electronic devices that operate at increasingly greater speeds. This demand for increased speed has resulted in a continual reduction in the size of semiconductor devices. Manufacturing of devices with smaller feature sizes introduces new challenges in many of the processes conventionally used in semiconductor fabrication. One of the most important of these fabrication processes is photolithography.
Photolithography is a commonly practiced process of creating a patterned mask on the surface of a semiconductor wafer so that subsequent patterned processes may be performed. During photolithography, a photoresist is deposited overlying a substrate and is patterned so that the pattern subsequently can be transferred to the underlying substrate by etching the substrate using the photoresist as an etch mask. Anti-reflective coatings (ARCs) are known and used to mitigate defects during the patterning of the substrate by attenuating or absorbing the light waves reflected from the substrate surface during photo exposure operations to improve image contrast. ARCs are of two types, that is, top anti-reflective coatings (TARCs) that reside overlying the photoresist and bottom anti-reflective coatings (BARCs) that are typically interposed between the substrate surface and the photoresist so as to serve as a barrier that inhibits the reflected waves from traversing back through the photoresist and adversely affecting the imaging process, which helps in defining images. Although some photoresist developer-soluble BARC materials exist, the majority of BARC materials require a plasma etch step to etch the BARC following lithographic patterning of the photoresist. Following plasma etch of the BARC, the underlying film (or films) is then etched typically through the use of a dry, plasma process.
With feature sizes continually shrinking in new device generations and with the use of porous dielectric materials to achieve low dielectric constant properties, the stripping or removal rate of the BARC from the patterned substrate is of growing importance. An improvement in the wet strip rate of BARCs used after feature patterning, that is, the rate of removal of any remaining BARC after plasma etching of the underlying substrate film(s), is necessary to preserve the post-dry etch critical dimensions as well as to minimize damage to the porous or otherwise low dielectric constant substrates if such films are present.
While various additives have been used to increase the wet strip rates of BARCs, they have proven unsatisfactory for a variety of reasons. For example, such additives may significantly increase the wet strip rates of a BARC but they must be added to the BARC in such high concentrations that, upon heating, they evaporate and create pores, voids or other defects that leave the BARC with an undesirably rough surface, which in turn introduces defects into the photolithography process. Typically, very high levels of additives that increase the BARC's wet strip rate also render it soluble in photoresist developer. Any loss of the BARC during patterning of the photoresist with photoresist developer leads to changes in the patterned critical dimensions of the photoresist or, worse, the complete loss of the photoresist features. In addition, some of the additives are added as solids to the BARC compositions used to form the BARCs, which solids prevent thin BARCs from being formed. Such additives also may prevent the BARC compositions from performing satisfactory via fill without unwanted voids. Further, such additives may adversely interfere with the adhesion properties of the BARC compositions relative to the materials upon which they are deposited, such as dielectric materials, or relative to the materials which are deposited on them, such as, other ARCs.
Accordingly, it is desirable to provide BARC compositions that result in BARCs that exhibit enhanced wet strip rates while also exhibiting resistance to photoresist developers. It also is desirable to provide BARC compositions that exhibit good adhesion properties and result in via fill with minimal voids. In addition, it is desirable to provide methods for fabricating such BARC compositions. Moreover, it is desirable to provide BARCs made from such BARC compositions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.